The small molecule GAT1508 activates brain-specific GIRK1/2 channel heteromers and facilitates conditioned fear extinction in rodents.

G-protein-gated inwardly-rectifying K (GIRK) channels are targets of G-protein-signaling systems that inhibit cell excitability. GIRK channels exist as homotetramers (GIRK2 and GIRK4) or heterotetramers with nonfunctional homomeric subunits (GIRK1 and GIRK3). Although they have been implicated in multiple conditions, the lack of selective GIRK drugs that discriminate among the different GIRK channel subtypes has hampered investigations into their precise physiological relevance and therapeutic potential.

Crh receptor priming in the bed nucleus of the stria terminalis (BNST) induces tph2 gene expression in the dorsomedial dorsal raphe nucleus and chronic anxiety.

The bed nucleus of the stria terminalis (BNST) is a nodal structure in neural circuits controlling anxiety-related defensive behavioral responses. It contains neurons expressing the stress- and anxiety-related neuropeptide corticotropin-releasing hormone (Crh) as well as Crh receptors. Repeated daily subthreshold activation of Crh receptors in the BNST is known to induce a chronic anxiety-like state, but how this affects neurotransmitter-relevant gene expression in target regions of the BNST is still unclear.

Assessment of fear and anxiety associated behaviors, physiology and neural circuits in rats with reduced serotonin transporter (SERT) levels.

Genetic variation in serotonin transporter (SERT) that reduces transcriptional efficiency is associated with higher anxiety and fear traits and a greater incidence of post traumatic stress disorder (PTSD). Although previous studies have shown that rats with no expression of SERT (SERT) have increased baseline anxiety behaviors, SERT rats with low SERT expression (and more relevant to the clinical condition with low SERT expression) do not. Yet, no systematic studies of fear acquisition/extinction or their underlying neural mechanisms have been conducted in this preclinical genetic SERT model.

Orexin Depolarizes Central Amygdala Neurons via Orexin Receptor 1, Phospholipase C and Sodium-Calcium Exchanger and Modulates Conditioned Fear.

Orexins (OX), also known as hypocretins, are excitatory neuropeptides with well-described roles in regulation of wakefulness, arousal, energy homeostasis, and anxiety. An additional and recently recognized role of OX is modulation of fear responses. We studied the OX neurons of the perifornical hypothalamus (PeF) which send projections to the amygdala, a region critical in fear learning and fear expression.

Select panicogenic drugs and stimuli induce consistent increases in tail skin flushes and decreases in core body temperature.

Panic attacks (PAs) are episodes of intense fear or discomfort that are accompanied by a variety of both psychological and somatic symptoms. Panic induction in preclinical models (e.g.

Evaluation of JNJ-54717793 a Novel Brain Penetrant Selective Orexin 1 Receptor Antagonist in Two Rat Models of Panic Attack Provocation.

Orexin neurons originating in the perifornical and lateral hypothalamic area are highly reactive to anxiogenic stimuli and have strong projections to anxiety and panic-associated circuitry. Recent studies support a role for the orexin system and in particular the orexin 1 receptor (OX1R) in coordinating an integrative stress response. However, no selective OX1R antagonist has been systematically tested in two preclinical models of using panicogenic stimuli that induce panic attack in the majority of people with panic disorder, namely an acute hypercapnia-panic provocation model and a model involving chronic inhibition of GABA synthesis in the perifornical hypothalamic area followed by intravenous sodium lactate infusion.

Electroacupuncture Promotes Central Nervous System-Dependent Release of Mesenchymal Stem Cells.

Electroacupuncture (EA) performed in rats and humans using limb acupuncture sites, LI-4 and LI-11, and GV-14 and GV-20 (humans) and Bai-hui (rats) increased functional connectivity between the anterior hypothalamus and the amygdala and mobilized mesenchymal stem cells (MSCs) into the systemic circulation. In human subjects, the source of the MSC was found to be primarily adipose tissue, whereas in rodents the tissue sources were considered more heterogeneous. Pharmacological disinhibition of rat hypothalamus enhanced sympathetic nervous system (SNS) activation and similarly resulted in a release of MSC into the circulation.

Anxiogenic CO2 stimulus elicits exacerbated hot flash-like responses in a rat menopause model and hot flashes in postmenopausal women.

Objective: As longitudinal studies determined that anxiety is a strong risk factor for hot flashes, we hypothesized that an anxiogenic stimulus that signals air hunger (hypercapnic, normoxic gas) would trigger an exacerbated hot flash-associated increase in tail skin temperature (TST) in a rat ovariectomy (OVEX) model of surgical menopause and hot flashes in symptomatic postmenopausal women. We also assessed TST responses in OVEX serotonin transporter (SERT) rats that models a common polymorphism that is associated with increased climacteric symptoms in postmenopausal women and increases in anxiety traits.

Methods: OVEX and sham-OVEX rats (initial experiment) and wildtype and SERT OVEX rats (subsequent experiment) were exposed to a 5-minute infusion of 20% carbon dioxide (CO2) normoxic gas while measuring TST.

Sustained relief of ongoing experimental neuropathic pain by a CRMP2 peptide aptamer with low abuse potential.

Uncoupling the protein-protein interaction between collapsin response mediator protein 2 (CRMP2) and N-type voltage-gated calcium channel (CaV2.2) with an allosteric CRMP2-derived peptide (CBD3) is antinociceptive in rodent models of inflammatory and neuropathic pain. We investigated the efficacy, duration of action, abuse potential, and neurobehavioral toxicity of an improved mutant CRMP2 peptide.

Evaluation of Low versus High Volume per Minute Displacement CO₂ Methods of Euthanasia in the Induction and Duration of Panic-Associated Behavior and Physiology.

Current recommendations for the use of CO ₂ as a euthanasia agent for rats require the use of gradual fill protocols (such as 10% to 30% volume displacement per minute) in order to render the animal insensible prior to exposure to levels of CO ₂ that are associated with pain. However, exposing rats to CO ₂ , concentrations as low as 7% CO ₂ are reported to cause distress and 10%-20% CO ₂ induces panic-associated behavior and physiology, but loss of consciousness does not occur until CO ₂ concentrations are at least 40%. This suggests that the use of the currently recommended low flow volume per minute displacement rates create a situation where rats are exposed to concentrations of CO ₂ that induce anxiety, panic, and distress for prolonged periods of time.

Hypothalamic orexin's role in exacerbated cutaneous vasodilation responses to an anxiogenic stimulus in a surgical menopause model.

Distressing symptoms such as hot flashes and sleep disturbances affect over 70% of women approaching menopause for an average of 4-7 years, and recent large cohort studies have shown that anxiety and stress are strongly associated with more severe and persistent hot flashes and can induce hot flashes. Although high estrogen doses alleviate symptoms, extended use increases health risks, and current non-hormonal therapies are marginally better than placebo. The lack of effective non-hormonal treatments is largely due to the limited understanding of the mechanisms that underlie menopausal symptoms.

Pharmacological depletion of serotonin in the basolateral amygdala complex reduces anxiety and disrupts fear conditioning.

The basolateral and lateral amygdala nuclei complex (BLC) is implicated in a number of emotional responses including conditioned fear and social anxiety. Based on previous studies demonstrating that enhanced serotonin release in the BLC leads to increased anxiety and fear responses, we hypothesized that pharmacologically depleting serotonin in the BLC using 5,7-dihydroxytryptamine (5,7-DHT) injections would lead to diminished anxiety and disrupted fear conditioning. To test this hypothesis, 5,7-DHT(a serotonin-depleting agent) was bilaterally injected into the BLC.

OREXIN 1 AND 2 RECEPTOR INVOLVEMENT IN CO2 -INDUCED PANIC-ASSOCIATED BEHAVIOR AND AUTONOMIC RESPONSES.

Background: The neuropeptides orexin A and B play a role in reward and feeding and are critical for arousal. However, it was not initially appreciated that most prepro-orexin synthesizing neurons are almost exclusively concentrated in the perifornical hypothalamus, which when stimulated elicits panic-associated behavior and cardiovascular responses in rodents and self-reported "panic attacks" and "fear of dying" in humans. More recent studies support a role for the orexin system in coordinating an integrative stress response.

A selective orexin-1 receptor antagonist attenuates stress-induced hyperarousal without hypnotic effects.

Orexins (OXs) are peptides produced by perifornical (PeF) and lateral hypothalamic neurons that exert a prominent role in arousal-related processes, including stress. A critical role for the orexin-1 receptor (OX1R) in complex emotional behavior is emerging, such as overactivation of the OX1R pathway being associated with panic or anxiety states. Here we characterize a brain-penetrant, selective, and high-affinity OX1R antagonist, compound 56 [N-({3-[(3-ethoxy-6-methylpyridin-2-yl)carbonyl]-3-azabicyclo[4.

Alcohol-preferring rats show decreased corticotropin-releasing hormone-2 receptor expression and differences in HPA activation compared to alcohol-nonpreferring rats.

Background: Corticotropin-releasing hormone (CRH) and urocortins (UCNs) bind to corticotropin-releasing hormone type 2 receptor (CRF2 receptor ), a Gs protein-coupled receptor that plays an important role in modulation of anxiety and stress responses. The Crhr2 gene maps to a quantitative trait locus (QTL) for alcohol preference on chromosome 4 previously identified in inbred alcohol-preferring (iP) and-nonpreferring (iNP) F2 rats.

Methods: Real-time polymerase chain reaction was utilized to screen for differences in Crhr2 mRNA expression in the central nervous system (CNS) of male iP and iNP rats.

Angiotensin II's role in sodium lactate-induced panic-like responses in rats with repeated urocortin 1 injections into the basolateral amygdala: amygdalar angiotensin receptors and panic.

Rats treated with three daily urocortin 1 (UCN) injections into the basolateral amygdala (BLA; i.e., UCN/BLA-primed rats) develop prolonged anxiety-associated behavior and vulnerability to panic-like physiological responses (i.

Group II metabotropic glutamate receptor type 2 allosteric potentiators prevent sodium lactate-induced panic-like response in panic-vulnerable rats.

Rats with chronic inhibition of GABA synthesis by infusion of l-allyglycine, a glutamic acid decarboxylase inhibitor, into their dorsomedial/perifornical hypothalamus are anxious and exhibit panic-like cardio-respiratory responses to treatment with intravenous (i.v.) sodium lactate (NaLac) infusions, in a manner similar to what occurs in patients with panic disorder.

Orexin, stress, and anxiety/panic states.

A panic response is an adaptive response to deal with an imminent threat and consists of an integrated pattern of behavioral (aggression, fleeing, or freezing) and increased cardiorespiratory and endocrine responses that are highly conserved across vertebrate species. In the 1920s and 1940s, Philip Bard and Walter Hess, respectively, determined that the posterior regions of the hypothalamus are critical for a "fight-or-flight" reaction to deal with an imminent threat. Since the 1940s it was determined that the posterior hypothalamic panic area was located dorsal (perifornical hypothalamus: PeF) and dorsomedial (dorsomedial hypothalamus: DMH) to the fornix.

Orexin 1 receptors are a novel target to modulate panic responses and the panic brain network.

Background: Although the hypothalamic orexin system is known to regulate appetitive behaviors and promote wakefulness and arousal (Sakurai, 2007 [56]), this system may also be important in adaptive and pathological anxiety/stress responses (Suzuki et al., 2005 [4]). In a recent study, we demonstrated that CSF orexin levels were significantly higher in patients experiencing panic attacks compared to non-panicking depressed subjects (Johnson et al.

Elevated tph2 mRNA expression in a rat model of chronic anxiety.

Background: Allelic variations in TPH2, the gene encoding tryptophan hydroxylase 2, the rate-limiting enzyme for brain serotonin (5-HT) biosynthesis, may be genetic predictors of panic disorder and panic responses to panicogenic challenges in healthy volunteers. To test the hypothesis that tph2 mRNA is altered in chronic anxiety states, we measured tph2 expression in an established rat model of panic disorder.

Methods: We implanted 16 adult, male rats with bilateral guide cannulae and then primed them with daily injections of the corticotropin-releasing factor (CRF) receptor agonist, urocortin 1 (UCN1, 6 fmoles/100 nl per side, n = 8) or vehicle (n = 8) into the basolateral amygdaloid complex (BL) for 5 consecutive days.

Activation of the orexin 1 receptor is a critical component of CO2-mediated anxiety and hypertension but not bradycardia.

Acute hypercapnia (elevated arterial CO(2)/H(+)) is a suffocation signal that is life threatening and rapidly mobilizes adaptive changes in breathing and behavioral arousal in order to restore acid-base homeostasis. Severe hypercapnia, seen in respiratory disorders (eg, asthma or bronchitis, chronic obstructive pulmonary disease (COPD)), also results in high anxiety and autonomic activation. Recent evidence has demonstrated that wake-promoting hypothalamic orexin (ORX: also known as hypocretin) neurons are highly sensitive to local changes in CO(2)/H(+), and mice lacking prepro-ORX have blunted respiratory responses to hypercapnia.

Suppression of inflammatory and neuropathic pain by uncoupling CRMP-2 from the presynaptic Ca²⁺ channel complex.

The use of N-type voltage-gated calcium channel (CaV2.2) blockers to treat pain is limited by many physiological side effects. Here we report that inflammatory and neuropathic hypersensitivity can be suppressed by inhibiting the binding of collapsin response mediator protein 2 (CRMP-2) to CaV2.

A selective, non-peptide CRF receptor 1 antagonist prevents sodium lactate-induced acute panic-like responses.

Corticotropin releasing factor (CRF) is implicated in a variety of stress-related disorders such as depression and anxiety, and blocking CRF receptors is a putative strategy for treating such disorders. Using a well-studied animal model of panic, we tested the efficacy of JNJ19567470/CRA5626, a selective, non-peptidergic CRF type 1 receptor (CRF1) antagonist (3, 10 and 40 mg/kg intraperitoneal injection), in preventing the sodium lactate (NaLac)-induced panic-like behavioural and cardiovascular responses. Adult male rats with chronic reduction of GABA levels (by inhibition of GABA synthesis with l-allyglycine, a glutamic acid decarboxylase inhibitor) in the dorsomedial/perifornical hypothalamus are highly anxious and exhibit physiological and behavioural responses to intravenous NaLac infusions similar to patients with panic disorder.

Changes in central sodium and not osmolarity or lactate induce panic-like responses in a model of panic disorder.

Panic disorder is a severe anxiety disorder characterized by recurrent panic attacks that can be consistently provoked with intravenous (i.v.) infusions of hypertonic (0.